Survival of small-spotted catshark (Scyliorhinus canicula) discarded by trawlers in the Cantabrian Sea

Published source details Rodríguez-Cabello C., fernández a., Olaso I. & Sánchez F. (2005) Survival of small-spotted catshark (Scyliorhinus canicula) discarded by trawlers in the Cantabrian Sea. Journal of the Marine Biological Association of the United Kingdom, 85, 1145-1150.
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This study is summarised as evidence for the following.

	Action	Category
	Reduce the duration of exposure to air of captured fish before release Action Link
	Release protected or species of concern alive after capture Action Link

Reduce the duration of exposure to air of captured fish before release

A replicated study in 2000–2001 of bottom fishing grounds in the Bay of Biscay, Spain (Rodríguez-Cabello et al. 2005) found that reducing air exposure under commercial fishing conditions did not increase the survival of unwanted small-spotted catshark Scyliorhinus canicular, but it was increased under research fishing conditions. Catshark survival rates were similar between exposure times (sorting time on deck) on commercial trawling trips (20 min: 82%, 30 min: 80%, 40 min: 78%, 60 min: 68%, 85 min: 64%). However, survival rates were improved with shorter times on deck during bottom trawl survey deployments (20 min: 100%, 30 min: 94%, 40 min: 92%, 60 min: 81%). The authors noted that although a weak effect was found under commercial conditions, survival did not appear to be affected by sorting time or tow duration (data reported as graphical analysis). Data were collected from otter trawl deployments during commercial fishing trips (16 hauls) and bottom trawl surveys (20 hauls). For each deployment, groups of twenty catshark were exposed to air: for six intervals between 18–85 min during commercial deployments and 20, 30, 40 and 60 min intervals during the trawl survey. Tow duration was 180–360 minutes for commercial deployments and 30 minutes during the survey. After each period of time on deck after capture, catshark were transferred to onboard tanks and survival was assessed after 1 h.

(Summarised by: Leo Clarke)
Release protected or species of concern alive after capture

A replicated study in 2000–2001 of bottom fishing grounds in the Cantabrian Sea, Spain (Rodríguez-Cabello et al. 2005) reported that a large proportion of unwanted (discarded) small-spotted catshark Scyliorhinus canicula survived after capture by commercial trawl nets. In commercial trawl catches, average catshark survival was 78% (range 47–91%). In addition, increases in sorting time during sorting of catches had a weak effect on survival (i.e. slightly decreased it), however there was no influence of haul duration (3–6 h; data reported as graphical analysis). In all but one haul there was no difference in survival between male and female catsharks (data reported as statistical results). Data were collected from otter trawl deployments during commercial fishing trips (16 hauls). For each deployment, groups of twenty catshark (10 of each sex) were selected and were exposed to air for roughly six different intervals between 18–85 min. After each interval, catshark were transferred to onboard tanks and survival was assessed after 1 h.

(Summarised by: Leo Clarke)